A national monument off Hawaii has became the world's largest marine reserve after it was expended by president Barack Obama, the White House announced.

The monument originally created by President George W Bush in 2006. The Papahanaumokuakea Marine National Monument will now span 1.5m sq km (582,578 sq miles), more than twice the size of Texas.

The commercial fishing and any new mining was banned by the designation.

According to the White House, the expansion aims to protect more than 7,000 species and enhance an ecosystem affected by ocean acidification and warming.

The expansion was welcomed by environmental campaigners. Joshua Reichert, an executive vice president at the Pew Charitable Trusts said that, "By expanding the monument, President Obama has increased protections for one of the most biologically and culturally significant places on the planet."

The Associated Press reported, Sean Martin, the president of the Hawaii Longline Association said that, "We are disappointed that the president has made a decision to close an area nearly the size of the entire state of Alaska without public process."

"This action will forever prohibit American fishermen from accessing those American waters. Quite a legacy indeed," he added.

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Nandini